import {
  ADD_NUMBER,
  SUB_NUMBER
} from './constants.js'

const initialState = {
  counter: 0
}

function reducer(state = initialState, action) {
  switch(action.type) {
    case ADD_NUMBER:
      return {...state, counter: state.counter + action.num}
    case SUB_NUMBER:
      return {...state, counter: state.counter - action.num}
    default:
      return state
  }
}

export default reducer